Debt (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,119,300,000	$ 3,119,300,000		$ 3,001,800,000
Revolving credit facility origination fees		(1,100,000)
Less unamortized discount	(3,800,000)	(3,800,000)		(4,300,000)
Debt Maturity Period	5 years 0 months 0 days
Proceeds from Issuance of Long-term Debt		300,000,000	0
Principal amount of senior notes outstanding	2,221,800,000	2,221,800,000
Debt Instrument, Maturity Date Range, Start		Sep. 01, 2016
Debt Instrument, Maturity Date Range, End		May 01, 2023
Senior Notes, stated interest rate, minimum (in hundredths)		5.25%
Senior Notes, stated interest rate, maximim (in hundredths)		6.875%
Revolving Credit Facility due 2016 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	297,500,000	297,500,000		480,000,000
Maturity date of long-term debt		Aug. 25, 2016
Borrowing capacity	1,500,000,000	1,500,000,000
Potential increased borrowing capacity	2,000,000,000	2,000,000,000
NumberOfMaturityDateExtensions	2	2
Additional period with in which maturity to be extended		1 year
Weighted-average interest rate (in hundredths)	2.22%	2.22%	2.56%
Amount outstanding	297,500,000	297,500,000
Letters of credit outstanding	3,800,000	3,800,000
Term Loan due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	600,000,000	600,000,000		300,000,000
Maturity date of long-term debt		Apr. 18, 2017
Additional period with in which maturity to be extended		1 year
Weighted-average interest rate (in hundredths)	2.26%	2.26%	2.23%
6.05% Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	176,800,000	176,800,000		176,800,000
Long-term debt, interest rate (in hundredths)	6.05%	6.05%
Maturity date of long-term debt		Sep. 01, 2016
6.80% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 134,000,000	$ 134,000,000		$ 134,000,000
Long-term debt, interest rate (in hundredths)	6.80%	6.80%
Maturity date of long-term debt		Apr. 01, 2018